Vehicle, display device and manufacturing method for a semiconductor device

ABSTRACT

To provide a semiconductor device in which a layer to be peeled is attached to a base having a curved surface, and a method of manufacturing the same, and more particularly, a display having a curved surface, and more specifically a light-emitting device having a light emitting element attached to a base with a curved surface. A layer to be peeled, which contains a light emitting element furnished to a substrate using a laminate of a first material layer which is a metallic layer or nitride layer, and a second material layer which is an oxide layer, is transferred onto a film, and then the film and the layer to be peeled are curved, to thereby produce a display having a curved surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitcomposed of thin film transistors (hereinafter referred to as TFTs)transferred by bonding a layer to be peeled off to a base member. Moreparticularly, the present invention relates to an electro-optical devicewhich is represented by a liquid crystal module, a light emitting devicewhich is represented by an EL module, and electronic equipment on whichsuch a device is mounted as a part. Further, the present inventionrelates to a manufacturing method of all these devices and apparatusesmentioned above.

Note that a semiconductor device in this specification indicates generaldevices functioning by utilizing semiconductor characteristics, and anelectro-optical device, a light emitting device, a semiconductorcircuit, and electronic equipment are all semiconductor devices.

2. Description of the Related Art

In recent years, a technique of constructing a thin film transistor(TFT) using a semiconductor thin film (about several to several hundrednm in thickness) formed on a substrate having an insulating surface hasbeen noted. The thin film transistor is widely applied to an electronicdevice such as an IC or an electro-optical device. In particular, thedevelopment of the thin film transistor as a switching element of animage display device is urgently necessary.

Further, concern over mounting, for example, a navigation system displaydevice, an audio operation screen display device and a measuring displaydevice into various display devices of vehicles such as an automobileand aircraft has been attempted.

Various applications utilizing such an image display device areexpected, and particularly its utilization in a portable device isnoted. Currently, a glass substrate or a quartz substrate is used forforming the TFT in many cases. However, there is a defect that the abovesubstrate is easy to crack and heavy. In addition, in the case of massproduction, it is difficult and thus not suitable to use a large sizeglass substrate and a large size quartz substrate. Thus, it is attemptedto form a TFT element on a flexible substrate, typically, a flexibleplastic film.

However, the plastic film has a low heat resistance, so that it isnecessary to reduce a maximum temperature of a process. As a result,under the current circumstances, a TFT having a preferable electricalcharacteristic cannot be formed on the plastic film as compared with thecase where the glass substrate is used. Therefore, a liquid crystaldisplay device and a light emitting element for which the plastic filmis used and which each have a high performance are not realized.

If a light emitting device in which an organic light emitting element(OLED: organic light emitting device) is formed or a liquid crystaldisplay device can be manufactured on a flexible substrate such as aplastic film, such a device can be used for a display having a curvedsurface, a show window and the like in addition to being thin and lightweight. Thus, its use is not limited to only a mobile device and thescope of application is very wide.

Further, if a display having a curved surface becomes available, in thecase where an imaging or measuring display is to be furnished in alimited space such as at the driver's seat in an automobile or aircraftor other such vehicle, the display can be mounted to various locationsthat have curved surfaces (such as the window, the ceiling, the door,the dashboard, etc.), thereby reducing the space occupied by thedisplay. Since the display has been a flat one up to now, space invehicles has been narrowed, or, complicated operations for embodying aflat display, such as operations for cutting off the walls, attachingand the like have been required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicein which a layer to be peeled off is bonded to a base member having acurved surface and a manufacturing method thereof. More particularly, anobject of the present invention is to provide a display having a curvedsurface, specifically, a light emitting device having a light emittingelement in which a layer containing an organic compound serves as alight emitting layer is bonded to the base member having a curvedsurface, or a liquid crystal display device in which a layer to bepeeled off is bonded to the base member having the curved surface.

Also, another object of the present invention is to provide asemiconductor device in which various elements (a thin film diode, aphotoelectric conversion element which is made of silicon and has a PINjunction, and a silicon resistor element) represented by a TFT arebonded to a flexible film (bendable film) and a manufacturing methodthereof.

According to the present invention, when forming a layer to be peeledoff containing an element onto a substrate, the channel lengthdirections of the regions functioning as channels for the element areall arranged in the same direction, and irradiation of laser light thatscans in the same direction as the channel lengths is performed, wherebythe element is completed. After that, the element is applied to a basehaving a curved surface curving in a different direction than theabove-mentioned channel length direction, that is, curving along thedirection of the channel width, and thus a display having a curvedsurface is realized. Note that, in the case where the peeled layer isapplied to the base with the curved surface, the peeled layer will alsobe curved along the curved surface of the base. In the presentinvention, all the channel length directions of the elements arearranged going in the same direction, while the channel lengthdirections and the direction that the base is curved are different.Therefore, even if the peeled layer containing the elements is curved,any influence on the characteristics of the elements can be kept at aminimum. In other words, it is also possible to provide a semiconductordevice that is sturdy with respect to deformation along a certaindirection (here meaning the direction along which the base is curved).

The construction of the invention with respect to a manufacturing methoddisclosed in the present specification is as follows:

That is, according to the present invention, there is provide amanufacturing method for a semiconductor device, including:

a step of forming a layer to be peeled off containing an element onto asubstrate;

a step of attaching a support to the layer peeled containing theelement, and then peeling the support from the substrate using physicalmeans; and

a step of attaching a transfer body to the layer to be peeled offcontaining the element, and sandwiching the element between the supportand the transfer body,

the method being characterized in that:

the element is a thin film transistor in which semiconductor layersoverlapping with a gate cathode while sandwiching an insulating filmtherebetween serve as channels, and the step of forming thesemiconductor layers includes a process of irradiating a laser lightthat scans in the same direction as channel length directions of thechannels.

However, according to the above-mentioned construction, if themechanical strength of the layer to be peeled off is sufficient, thetransfer body which anchors the layer to be peeled off may not need tobe attached.

Note that, the above-mentioned construction is characterized in that aplurality of the thin film transistors are provided, and the channellength directions of the plurality of thin film transistors are allarranged in the same direction.

Further, the above-mentioned construction is characterized in that theabove-mentioned support has a curved surface that is curved in a convexor concave shape, and the direction in which the above-mentioned supportis curved and the direction of the above-mentioned channel lengths aredifferent from each other. Further, in the case where a transfer body isto be attached, the transfer body also has a curved surface that iscurved in a concave or convex shape fitting with the curved surface ofthe support. Therefore, the above-mentioned construction ischaracterized in that the above-mentioned transfer body has the concaveor convex curved surface, and the direction in which the above-mentionedsupport is curved and the direction of the above-mentioned channellengths are different.

Further, the above-mentioned construction is characterized in that whenit is formed as a liquid crystal display device, the above-mentionedsupport is an opposing substrate, the above-mentioned element has apixel electrode, and the space between the pixel electrode and theopposing substrate is filled with a liquid crystal material.

Further, the above-mentioned construction is characterized in that whenit is formed as a light emitting device having a light emitting elementin which a layer containing an organic compound serves as a lightemitting layer, the above-mentioned support is a sealing material, andthe above-mentioned element is the light emitting element.

Further, according to the above-mentioned construction, the method ofperforming the peeling is not particularly restricted, and it ispossible to use a method in which a separation layer is provided betweenthe layer to be peeled off and the substrate, and the separation layeris removed by means of a chemical solution (an etchant) to separate thelayer to be peeled off and the substrate, or a method in which aseparation layer constituted of amorphous silicon (or polysilicon) isprovided between the layer to be peeled off and the substrate, and laserlight is irradiated through the substrate to expel hydrogen contained inthe amorphous silicon, whereby gaps are created and the layer to bepeeled off and the substrate are thus separated. Note that, in the casewhere the laser light is used for the peeling, the elements contained inthe layer to be peeled off should be formed with the thermal processingtemperature set at 410° C. or less so that the hydrogen is not expelledbefore the peeling.

Further, as another method of peeling, it is also possible to use apeeling method in which film stress occurring between two layers isutilized to perform the peeling. In this peeling method, a metalliclayer, preferably a nitrided metallic layer, is provided onto thesubstrate, and then an oxidized layer is provided contacting theabove-mentioned nitrided metallic layer, so that the element is formedonto the oxidized layer. In this case, the film will not peel off evenduring the film application processing or during thermal processing atover 500° C., and a clean separation within the oxidized layer or at itssurface can be achieved easily with a physical means. Further, in orderto further the peeling, thermal processing or laser radiation processingmay be performed before performing the peeling with the above-mentionedphysical means.

According to the manufacturing method of the present invention formanufacturing a semiconductor device using a peeling method in whichfilm stress occurring between the two layers is utilized to perform thepeeling, there is provided a method of manufacturing a semiconductordevice, characterized by including:

a first step of forming onto a first substrate a layer to be peeled offthat contains a semiconductor element;

a second step of adhering a second substrate to the layer to be peeledoff with a first adhesive, and sandwiching the layer to be peeled offbetween the first substrate and the second substrate;

a third step of separating the layer to be peeled off and the firstsubstrate;

a fourth step of adhering a third substrate to the layer to be peeledoff with a second adhesive, and sandwiching the layer to be peeled offbetween the second substrate and the third substrate;

a fifth step of separating the layer to be peeled off and the secondsubstrate, and forming the layer to be peeled off, for which the secondadhesive and the third substrate serve as a support; and

a sixth step of curving the third substrate.

According to the above-mentioned construction, in the fifth step, thefirst adhesive is dissolved in a solvent and removed, and the layer tobe peeled off and the second substrate are separated, or alternativelythe first adhesive is a photosensitive adhesive, and, in the fifth step,light is irradiated to separate the layer to be peeled off and thesecond substrate. Further, it is desirable that the first substrate andthe second substrate are materials which are more rigid than the thirdsubstrate, and the third substrate is a substrate which is bendable.

Note that, also in the above-mentioned construction, it is preferablethat the above-mentioned semiconductor element is a thin film transistorin which a semiconductor layer that overlaps the gate electrode whilesandwiching an insulating film therebetween serves as a channel, and thesteps of forming the above-mentioned semiconductor layer involveradiating a laser light which scans in the same direction as the channellength direction of the above-mentioned channel.

According to the manufacturing method of the present invention formanufacturing a semiconductor device having a light emitting element inwhich a layer containing an organic compound serves as a light emittinglayer, by using a peeling method in which film stress occurring betweenthe two layers is utilized to perform the peeling, there is provided amethod of manufacturing a semiconductor device, characterized byincluding:

a first step of forming onto a first substrate a layer to be peeled offthat contains one of a semiconductor element and a light emittingelement in which a layer containing an organic compound serves as alight emitting layer;

a second step of adhering a second substrate to the layer to be peeledoff with a first adhesive, and sandwiching the layer to be peeled offbetween the first substrate and the second substrate to which a film isapplied;

a third step of separating the layer to be peeled off and the firstsubstrate;

a fourth step of adhering a third substrate to the layer to be peeledoff with a second adhesive, and sandwiching the layer to be peeled offbetween the second substrate and the third substrate;

a fifth step of separating the film and the second substrate, andforming the layer to be peeled off, for which the film, the secondadhesive and the third substrate serve as a support; and

a sixth step of curving the third substrate.

According to the above-mentioned construction, the film is a tape havinga photosensitive adhesive on one or both sides thereof, and, in thefifth step, light is irradiated to separate the film and the secondsubstrate. Further, it is desired that the first substrate and thesecond substrate are materials which are more rigid than the thirdsubstrate, and the third substrate is a substrate which is bendable.

Note that, also in the above-mentioned construction, it is preferablethat the above-mentioned semiconductor element is a thin film transistorin which a semiconductor layer that overlaps the gate electrode whilesandwiching an insulating film therebetween serves as a channel, and thesteps of forming the above-mentioned semiconductor layer involveradiating a laser light which scans in the same direction as the channellength direction of the above-mentioned channel.

The semiconductor device obtained according to the above-mentionedmanufacturing method of the present invention as described above, hasvarious characteristics.

First construction of the present invention as disclosed in the presentspecification relates to a semiconductor device, characterized in that aplurality of thin film transistors are provided on a base having acurved surface curved in a concave or convex shape, and the channellength directions of the thin film transistors are all arranged in thesame direction, and the above-mentioned channel length directions run ina different direction from the direction in which the above-mentionedbase is curved.

Further, the present invention may also be applied in a case wheredifferent thin film transistors are formed to a pixel portion and to adrive circuit, respectively. That is, according to second constructionof the invention that represents another construction thereof, there isprovided a semiconductor device, characterized in that a pixel portionand a drive circuit portion are formed onto a substrate having a curvedsurface that is curved in a concave or a convex shape and the channellength direction of a thin film transistor provided to theabove-mentioned pixel portion and the channel length direction of a thinfilm transistor provided to the drive circuit portion are arranged so asto run in the same direction, and the above-mentioned channel lengthdirection is different from the direction in which the base is curved.Note that, the design rule of this pattern is approximately from 5 to 20μm, and approximately 10⁶ to 10⁷ TFTs are built onto the substrate forthe drive circuit and for the pixel portion, respectively.

Further, each of the above-mentioned constructions is characterized inthat the above-mentioned channel length direction is the same directionas the scanning direction by the laser light that is irradiated onto thesemiconductor layer of the above-mentioned thin film transistor. In acase where the channel for the thin film transistor is formed using asemiconductor film that is crystallized on the substrate by laserannealing, when the crystal growth direction and the carrier's movementdirection are aligned with each other, high field effect mobility can beobtained. In other words, by aligning the crystal formation directionand the channel length direction, the field effect mobility can beraised substantially. In a case where a continuously oscillating laserbeam is irradiated onto a non-monocrystal semiconductor film to achievethe crystallization, the liquid/solid boundary can be maintained andcontinuous crystal growth can be achieved along the laser beam's scandirection. For the laser light, it is possible to use a gas laser suchas an excimer laser, a solid-state laser such as a YAG laser, or asemiconductor laser. Further, the laser oscillation may be eithercontinuous oscillation or pulse oscillation, and the shape of the laserbeam may be linear or rectangular.

Further, each of the above-mentioned constructions is characterized inthat the above-mentioned curving direction and the above-mentionedchannel length direction run perpendicular to each other. That is, thedirection perpendicular to the channel length direction is the channelwidth direction, and third construction of the present invention whichrepresents another construction thereof relates to a semiconductorcharacterized in that a plurality of thin film transistors are providedonto a base having a curved surface that is curved in a concave or aconvex shape, the channel width directions of the plurality of thin filmtransistors are all arranged in the same direction, and theabove-mentioned channel width directions run in the same direction asthe direction in which the above-mentioned base is curved.

Note that, in the above-mentioned third construction, theabove-mentioned channel width direction is perpendicular to the scandirection of the laser light irradiated onto the semiconductor layer ofthe above-mentioned thin film transistor.

Further, the base with the curved surface is curved in a concave or aconvex shape. When it is curved in a certain single direction, it can besaid that the base has a curved surface with a curvature along onedirection, and with no curvature along another direction. Therefore,fourth construction of the present invention which represents anotherconstruction thereof relates to a semiconductor device, characterized inthat the channel length directions of a plurality of thin filmtransistors provided onto a surface of a base having a curved surfacewith a curvature along one direction and with no curvature along anotherdirection are all arranged in the same direction, and theabove-mentioned channel length directions and the direction withoutcurvature run in the same direction.

Note that, the above-mentioned fourth construction is characterized inthat the above-mentioned channel length direction is the same directionas the scan direction of the laser light irradiated onto thesemiconductor layers of the above-mentioned thin film transistors.

Further, the present invention can be applied to a flexible film (a filmthat can be curved), and is more preferably applied in a case where thepeeled layer is applied to a film that is curved in one direction. Notethat, the flexible film is not curved when in its normal state, butrather is curved in a certain direction by means of some external force.Thus, fifth construction of the present invention which representsanother construction thereof relates to a semiconductor device,characterized in that a plurality of thin film transistors are providedonto a base that can be curved into a concave shape or a convex shape,the channel length directions of the plurality of thin film transistorsare all arranged in the same direction, and the direction in which theabove-mentioned base is bent and the above-mentioned channel lengthdirection are different from each other.

Note that, the above-mentioned fifth construction is characterized inthat the above-mentioned channel length directions are the samedirection as the scan direction of laser light that is irradiated ontothe semiconductor layers of the thin film transistors. Further, in theabove-mentioned fifth construction, the above-mentioned curved directionand the above-mentioned channel length directions cross each otherperpendicularly, which is to say that the above-mentioned curveddirection and the channel width directions run in the same direction.

Note that, in the present specification, the transfer body refers to abase which is adhered to the peeled layer after the peeling, and,provided that it has a curved surface, it may be formed of plastic,glass, metal, ceramic or a material of any other composition withoutrestriction. Further, in the present specification, the support refersto a base which is adhered to the layer to be peeled off when thepeeling is performed with the physical means, and it may be formed ofplastic, glass, metal, ceramic or a material of any other compositionwithout particular restriction. Further, the shape of the transfer bodyand the shape of the support are not particularly restricted, and theymay have flat surfaces, they may have curved surfaces, they may becurved, and they may be film shaped. Further, if light-weight is to begiven top priority, then a film-shape plastic substrate is desirable,such as, for example, polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC),nylon, polyether ether ketone (PEEK), polysulfone (PSF), polyether imide(PEI), polyarilate (PAR), polybutylene terephthalate (PBT) and the like.

Further, the above-mentioned respective manufacturing methods enablerealization of a display having a curved surface, which can be mountedin a vehicle such as an automobile, an aircraft, a seagoing vessel, atrain, and the like. An interior wall, ceiling, or other part of thevehicle is formed of a smooth and curved surface so that the large openspace can be secured inside the vehicle and no problem occurs even whena person's body bumps into it for some reason. Thus, Construction 6 ofthe present invention which represents another construction thereofrelates to a vehicle in which there is mounted a display device having athin film transistor and a light emitting element in which a layercontaining an organic compound serves as a light emitting layer, as ameasuring instrument or as an illumination device. The display devicehaving the thin film transistor and the light emitting element in whicha layer containing an organic compound serves as a light emitting layeris preferably of an active matrix-type, but it is also possible tomanufacture a passive-type display device as well.

For example, a window of the vehicle may be used as the base, and thedisplay device having the light emitting element in which a layercontaining an organic compound serves as a light emitting layer may becurved and adhered to fit the curved surface of the window, therebyenabling display of an image or of a measuring instrument. Moreparticularly, the display device having the light emitting element inwhich a layer containing an organic compound serves as a light emittinglayer can be made extremely thin and lightweight, such that the spaceinside the vehicle is not altered. In the case where the display devicehaving the light emitting element in which a layer containing an organiccompound serves as a light emitting layer is attached to the window ofthe vehicle, it is desirable that the substrate, the electrodes and thewiring be transparent, and a film for blocking external light may alsobe provided. Further, it is desirable that the scenery of the outsidecan be viewed without obstruction when a display is not being performed.

Further, display of an image or a measuring instrument can also beperformed when the display having the light emitting element in whichthe layer containing the organic compound serves as the light emittinglayer is curved and attached along the interior wall, door, seat ordashboard of the vehicle. Since it is sufficient simply to attach theflexible display device of the present invention along a curved surface,the process of installing the display device is simple, and it is notparticularly necessary to perform local machining of the interior wall,door, seat, or dashboard portion. Further, in an automobile, forexample, if the automobile is driven from the right-hand side, there isa blind spot on the rear left side since a portion of the vehicle body(a portion between the windows) exists there. However, if the flexibledisplay device of the present invention is attached to the portionbetween the windows and a camera capable of capturing the blind spot isattached on the exterior of the vehicle, and the display device and thecamera are attached to each other, then the driver can confirm the blindspot. In particular, the display device having the light emittingelement in which the layer containing the organic compound materialserves as the light emitting layer can handle moving images better thana liquid crystal display, and provides a display device with a widefield of vision.

Further, by using the ceiling of the vehicle as the base and curving andattaching the display device having the light emitting element in whichthe layer containing the organic compound material serves as the lightemitting layer along the curved surface of the ceiling, it becomespossible to perform an image display and interior lighting. Further, inan automobile, for example, if the flexible display device of thepresent invention is attached to the portions between the windows andthen a camera corresponding to each of the display devices and capableof capturing the outside view is mounted onto the exterior of the carand the displays and the camera are attached to each other, then thepeople inside the vehicle can enjoy the scenery of the outside as if ina convertible car with the roof down, even though they are inside thevehicle. Further, in a train or electric train, for example, if theflexible display device of the present invention is attached to a widowand/or wall, then advertisements and television images can be displayedwithout reducing the open space within the train. More particularly, thedisplay device having the light emitting element in which the layercontaining the organic compound material serves as the light emittinglayer provides a display device offering a wider field of vision than aliquid crystal display device.

In the above-mentioned vehicle, if the radius of curvature of themounted display device is from 50 cm to 200 cm, then the thin filmtransistors and the light emitting element in which the layer containingthe organic compound material serves as the light emitting layer can bedriven without problems. Note that, it is preferable that the channellength directions of the plural thin film transistors that are providedare all arranged in the same direction, and the above-mentioned channellength direction is different from the direction in which theabove-mentioned base is curved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C are diagrams of steps illustrating an embodiment mode ofthe present invention;

FIG. 2 is a diagram indicating directional orientations in an embodimentmode of the present invention;

FIG. 3 is a layout diagram showing a configuration of a laser radiationdevice, according to Embodiment 1 of the present invention;

FIG. 4 is another layout diagram showing a configuration of a laserradiation device, according to Embodiment 1 of the present invention;

FIG. 5 is a diagram for explaining a construction of a substrateprovided with a TFT, and the relationship between an arrangement of asemiconductor area constituting the TFT and a scan direction of a laserbeam;

FIG. 6A to 6D are diagrams for explaining the laser beam scan directionalong a semiconductor film, and steps of manufacturing a top gate-typeTFT;

FIG. 7A to 7D are diagrams for explaining the laser beam scan directionalong the semiconductor film, and steps of manufacturing a bottomgate-type TFT;

FIGS. 8A to 8G are diagrams of steps illustrating Embodiment 3 of thepresent invention;

FIG. 9 is a diagram illustrating V-I characteristics of an nchannel-type TFT after peeling;

FIG. 10 is a diagram illustrating V-I characteristics of a pchannel-type TFT after peeling;

FIGS. 11A to 11F are diagrams of steps illustrating Embodiment 4 of thepresent invention;

FIGS. 12A and 12B are external views of a curved semiconductor devicehaving a light emitting element in which a layer containing organicmaterial serves as the light emitting layer, according to Embodiment 4of the present invention;

FIG. 13 is a diagram showing the vicinity in front of a driver's seat ina car, according to Embodiment 5 of the present invention;

FIG. 14 is a diagram showing the rear portion behind the car, accordingto Embodiment 5 of the present invention; and

FIGS. 15A to 15D are diagrams of steps illustrating Embodiment 6 of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment mode of the present invention will be described below.

Hereinafter, a typical manufacturing order according to the presentinvention will be briefly described using FIGS. 1A to 1C and 2.

In FIG. 1A, reference numeral 10 denotes a substrate, 11 a denotes alayer to be peeled, 12 denotes a pixel portion provided to the layer tobe peeled, 13 a denotes a semiconductor layer provided in the pixelportion, 13 b denotes a channel length direction of the semiconductorlayer 13 a, 14 a denotes a laser light irradiation area, and 14 bdenotes a laser light irradiation direction.

FIG. 1A shows a manufacturing step indicating the course of a completionof the layer to be peeled and is a schematic view indicating processingfor irradiating laser light to the semiconductor layer. Lasercrystallization and laser annealing can be conducted by the laser lightirradiation processing. An oscillation mode may be either continuousoscillation or pulse oscillation. In order to continuously producecrystal growth with a molten state of the semiconductor film, it isdesirable that a continuous oscillation mode is selected.

In FIG. 1A, all channel length directions of a large number ofsemiconductor layers included in the layer to be peeled are aligned withthe same direction. In addition, assume that the laser light irradiationdirection, that is, a scanning direction is the same direction as thechannel length directions. Thus, when the crystal growth direction isaligned with the channel length direction, the field effect mobility canbe substantially increased. Note that the example in which linear laserlight irradiation is conducted is shown in FIG. 1A. However, the presentinvention is not particularly limited to this. In addition, here, thelaser light irradiation is conducted after patterning the semiconductorlayer. The laser light irradiation may be conducted before thepatterning.

Next, various elements (such as a thin film diode, a photoelectricconversion element which is made of silicon and has a PIN junction, anda silicon resistor element) represented by a TFT are produced by formingelectrodes, wirings, an insulating film, and the like to complete thelayer to be peeled 11 b, and then the layer to be peeled 11 b is peeledfrom the substrate 10.

Note that the peeling method is not particularly limited. Here, apeeling method utilizing film stresses of a metallic layer or a nitridelayer and an oxide layer is used as a peeling method which is notlimited by a heat treatment temperature and a kind of substrate. First,before the state shown in FIG. 1A is obtained, a nitride layer or ametallic layer (not shown) is formed on the substrate 10. A typicalexample of the nitride layer or the metallic layer includes a singlelayer made of an element selected from the group consisting of Ti, W,Al, Ta, Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, and Pt, or analloy material or a compound material which contains mainly the element,or a laminate of those. In addition, a single layer made of nitridecontaining the element, for example, titanium nitride, tungsten nitride,tantalum nitride, or molybdenum nitride, or a laminate of those may beused. Next, an oxide layer (not shown) is formed on the nitride layer orthe metallic layer. For a typical example of the oxide layer, a siliconoxide material, a silicon oxynitride material, or a metallic oxidematerial may be used. Note that the oxide layer may be formed by anyfilm formation method such as a sputtering method, a plasma CVD method,or an applying method. It is important that film stress of the oxidelayer is different from that of the nitride layer or the metallic layer.The respective film thicknesses are preferably set as appropriate in arange of 1 nm to 100 nm, thereby adjusting respective film stresses. Inaddition, an insulating layer or a metallic layer may be providedbetween the substrate and the nitride layer or the metallic layer toimprove the contact property to the substrate 10. Next, a semiconductorlayer is preferably formed on the oxide layer to obtain the layer to bepeeled 11 a. Note that, according to the above peeling method, even ifthe film stress of the oxide layer is different from that of the nitridelayer or the metallic layer, film peeling or the like is not caused byheat treatment in a manufacturing step for the layer to be peeled. Inaddition, according to the above peeling method, the film stress of theoxide layer is different from that of the nitride layer or the metalliclayer. Thus, peeling can be produced by relatively small force. Inaddition, the example in which the layer to be peeled 11 b having asufficient mechanical strength is assumed is indicated here. When themechanical strength of the layer to be peeled 11 b is insufficient, itis preferable that peeling is conducted after a support member (notshown) for fixing the layer to be peeled 11 b is bonded thereto. Notethat, when the layer to be peeled 11 b is peeled, it is important toprevent a bend of the layer to be peeled 11 b so that a crack is notcaused in the layer to be peeled.

Thus, the layer to be peeled 11 b which is formed on the oxide layer canbe separated from the substrate 10. A state obtained after peeling isshown in FIG. 1B. In a stage shown in FIG. 1B, not only thesemiconductor layer but also electrodes, wirings, and the like areformed. However, for simplification, they are not shown here.

The peeled layer 11 c can be bent. A state obtained after the bending isshown in FIG. 1C. The peeled layer 11 c is bent in a bending direction19. It is needless to say that the peeled layer can be bonded to atransfer body (not shown) having a curved surface.

In FIG. 1C, reference numeral 15 denotes a driver circuit (X-direction),16 a denotes a semiconductor layer provided in the driver circuit(X-direction), 16 b denotes a channel length direction of thesemiconductor layer 16 a, 17 denotes a driver circuit (Y-direction), 18a denotes a semiconductor layer provided in the driver circuit(Y-direction), and 18 b denotes a channel length direction of thesemiconductor layer 18 a.

Thus, the maximum feature of the present invention is that the laserlight irradiation direction 14 b and the channel length directions 13 b,16 b, and 18 b of all the semiconductor layers provided in the layer tobe peeled are set to be the same direction, and these directions and abending direction 19 are set to be orthogonal to each other.

Note that, in order to further clear a correlation among thesedirections, the case where a TFT is noted is shown in FIG. 2. FIG. 2briefly shows a TFT having a semiconductor layer 20, a gate electrode21, and electrodes (source electrode and drain electrode) 22 and 23.Note that the TFT can be produced as follows by using a known technique.First, a semiconductor film having an amorphous structure (made ofamorphous silicon or the like) is crystallized by a knowncrystallization technique to produce a semiconductor film having acrystalline structure (made of polysilicon or the like), and thenpatterned into a predetermined shape to form the semiconductor layer 20.Next, the semiconductor layer 20 is covered with a gate insulating film(not shown) and then the gate electrode 21 is formed so as to partiallyoverlap the semiconductor layer 20 through the insulating filminterposed therebetween. After that, an impurity element for impartingan n-type or p-type conductivity is added to a portion of thesemiconductor layer to produce a source region and a drain region, aninterlayer insulating film (not shown) covering the gate electrode isformed, and the electrodes (source electrode and drain electrode) 22 and23 electrically connected with the source region and the drain regionare formed on the interlayer insulating film.

In the present invention, laser light whose scanning direction is ascanning direction 25 shown in FIG. 2 is used for manufacturing the TFT.In addition, a portion of the semiconductor layer 20 which is overlappedwith the gate electrode 21 through the gate insulating film interposedtherebetween serves as a channel. Thus, a channel length directionbecomes a channel length direction 24 shown in FIG. 2. The scanningdirection 25 of laser light becomes the same direction as the channellength direction 24. In addition, a channel width direction which is adirection orthogonal to the channel length direction 24 is the samedirection as a bending direction. The bending direction becomes abending direction 26 shown in FIG. 2. Note that the example of a topgate TFT is shown in FIG. 2. The present invention can be applied to,for example, a bottom gate (inverse staggered) TFT or a staggered TFTindependent on the TFT structure.

Although a TFT in which a semiconductor layer containing silicon servesas an active layer is shown here, but it is not limited to such a TFTparticularly. It is also possible to manufacture an organic TFT in whichan active layer is made of an organic material. Materials for the activelayer of an organic TFT can be a material having considerable amount ofcarbon when it is combined with other materials, or a materialcontaining an isotope of carbon element except diamond. Asrepresentative materials of the active layer of an organic TFT, C₆₀,C₇₀, thiophene polymer, thiophene substitution derivatives, poly(thienylene vinylene) and the like can be exemplified.

Also, the present invention can be applied to various manufacturingmethods of semiconductor device. Particularly, when a plastic substrateis used for the transfer body and the support member, weight reductioncan be realized.

When a liquid crystal display device is manufactured, it is preferablethat the support member is used as a counter substrate and bonded to thelayer to be peeled using a sealing member as a bonding layer. In thiscase, the element provided to the layer to be peeled has a pixelelectrode. A liquid crystal material is filled into a space between thepixel electrode and the counter substrate. In addition, an order formanufacturing the liquid crystal display device is not particularlylimited. For example, the counter substrate as the support member isbonded to the layer to be peeled which is provided to the substrate, aliquid crystal material is injected therebetween, and then the substrateis peeled and the plastic substrate as the transfer body is bonded tothe layer to be peeled. Alternatively, after the pixel electrode isformed, the substrate is peeled, the plastic substrate as a firsttransfer body is boned to the layer to be peeled, and then the countersubstrate as a second transfer body is bonded thereto.

Also, when a light emitting device represented by a device having alight emitting element in which a layer containing an organic compoundserves as a light emitting layer is manufactured, it is preferable thatthe support member is used as a sealing member. Thus, a light emittingelement is completely shielded from external so as to prevent entranceof a substance such as moisture or oxygen for promoting deterioration ofan organic compound layer from external. In addition, when the lightemitting device represented by the device having a light emittingelement in which a layer containing an organic compound serves as alight emitting layer is manufactured, as in the case of the supportmember, it is preferable that the transfer body sufficiently preventsentrance of a substance such as moisture or oxygen for promotingdeterioration of an organic compound layer from external. In addition,an order for manufacturing the light emitting device is not particularlylimited. For example, after the light emitting element is formed, aplastic substrate as the support member is bonded to the layer to bepeeled which is provided to a substrate, the substrate is peeled, and aplastic substrate as the transfer body is bonded to the layer to bepeeled. Alternatively, after the light emitting element is formed, thesubstrate is peeled, a plastic substrate as a first transfer body isboned to the layer to be peeled, and then a plastic substrate as asecond transfer body is bonded thereto. In addition, when it isimportant to suppress the deterioration occurring due to transmission ofmoisture or oxygen, a thin film is formed in contact with the layer tobe peeled after peeling to repair a crack caused at peeling. When a filmhaving thermal conductivity, specifically, an aluminum nitride or analuminum oxynitride is used as the thin film which is in contact withthe layer to be peeled, in addition to an effect for radiating heatgenerated in the element to suppress the deterioration thereof, aneffect for preventing deformation or degradation of, the transfer body,specifically, a plastic substrate can be obtained. In addition, the filmhaving thermal conductivity has an effect for preventing mixing of animpurity such as moisture or oxygen from external.

The present invention made by the above constitutions will be describedin more detail through the following embodiments.

Embodiment 1

Here, an example of laser processing apparatus applicable to the presentinvention will be described.

Crystallization of amorphous silicon by laser annealing is conductedthrough a melting-solidification process. More specifically, the casewhere it is divided into two stages, that is, a stage of generation ofcrystal nucleus and a stage of crystal growth from the nucleus isconsidered. However, in the case of laser annealing using a pulse laserbeam, a generation position of crystal nucleus and a generation densitythereof cannot be controlled but left to natural generation. Thus, acrystal grain is formed at an arbitrary position within the surface of aglass substrate and only a small size of about 0.2 μm to 0.5 μm isobtained. A large number of defects are caused in a crystal boundary.This is considered to be a factor limiting the field effect mobility ofa TFT.

It is considered that a method of conducting crystallization withmelting-solidification by continuous oscillation laser scanning is amethod similar to a zone melting method. However, according to themethod, a large beam size cannot be obtained. In addition, it is obviousthat much time is required for achieving crystallization over the entiresurface of a large area substrate.

In this embodiment, a laser processing apparatus for conducting laserbeam irradiation with a state in which an irradiation position issubstantially aligned with a position in which a TFT is produced, overthe entire surface of a large area substrate for crystallization, sothat a crystalline semiconductor film having a large grain size can beformed at high throughput will be described below.

As a laser irradiation apparatus of Embodiment 1, the followingapparatus may be used. The laser irradiation apparatus includes a firstmovable mirror for deflecting a laser beam in a main scanning directionand a second movable mirror for receiving the laser beam deflected inthe main scanning direction and conducting scanning in a sub scanningdirection, which is a long shape. The second movable mirror has meansfor scanning a laser beam in the sub scanning direction at a rotationangle about the axis of the long shape direction as a center toirradiate the laser beam to an object to be processed which is placed ona stage.

Also, as another laser irradiation apparatus, the following apparatusmay be used. That is, the laser irradiation apparatus includes a firstlaser beam scanning system and a second laser beam scanning system. Thefirst laser beam scanning system has a first movable mirror fordeflecting a laser beam in a first main scanning direction and a longsecond movable mirror for receiving the laser beam deflected in thefirst main scanning direction and conducting scanning in a first subscanning direction. The second laser beam scanning system has a thirdmovable mirror for deflecting a laser beam in a second main scanningdirection and a long fourth movable mirror for receiving the laser beamdeflected in the second main scanning direction and conducting scanningin a second sub scanning direction. The second movable mirror has meansfor scanning a laser beam in the first sub scanning direction at arotation angle about the axis of the long shape direction as a center toirradiate the laser beam to an object to be processed which is placed ona stage. The fourth movable mirror has means for scanning a laser beamin the second sub scanning direction at a rotation angle about the axisof the long shape direction as a center to irradiate the laser beam tothe object to be processed which is placed on the stage.

In the above configuration, a galvanomirror or a polygon mirror isapplied to the first and second movable mirrors. A solid laser or a gaslaser is preferably applied to a laser for providing the laser beam.

In the above configuration, a laser beam is scanned in the main scanningdirection by the first movable mirror and scanned in the sub scanningdirection by the second movable mirror. Thus, the laser beam can beirradiated in an arbitrary position onto the object to be processed. Inaddition, a plurality of such laser beam scanning means are provided andlaser beams are irradiated to a surface to be formed in biaxialdirections. Thus, a laser processing time can be shortened.

Hereinafter, a laser irradiation apparatus of this embodiment will bedescribed with reference to the drawings.

FIG. 3 shows a desirable example of a laser processing apparatus of thisembodiment. The shown laser processing apparatus includes a solid laser101 capable of conducting continuous oscillation or pulse oscillation, alens such 102 as a collimator lens or a cylindrical lens for condensinga laser beam, a fixed mirror 103 for changing an optical path of thelaser beam, a galvanomirror 104 for radially scanning the laser beam ina two-dimensional direction, and a movable mirror 105 for receiving thelaser beam by the galvanomirror 104 and irradiating the laser beamtoward a surface to be irradiated of a stage 106. An optical axis of thegalvanomirror 104 and that of the movable mirror 105 are intersectedeach other and rotated in arrow directions shown in FIG. 3,respectively. Thus, a laser beam can be scanned over the entire surfaceof a substrate 107 placed on the stage 106. When the movable mirror 105is used as an fθ mirror to correct an optical path difference, a beamshape on a surface to be irradiated can be also adjusted.

FIG. 3 shows a system for scanning a laser beam in a uniaxial directionof the substrate 107 placed on the stage 106 by the galvanomirror 104and the movable mirror 105. As a more preferable configuration, as shownin FIG. 4, a half mirror 108, a fixed mirror 109, a galvanomirror 110,and a movable mirror 111 is added to the configuration shown in FIG. 3,and laser beams may be simultaneously scanned in biaxial directions (X-and Y-directions). A processing time can be shortened by using such aconfiguration. Note that the galvanomirrors 104 and 110 may be replacedby polygon mirrors.

A solid laser is preferable as the laser, and a solid laser usingcrystal such as YAG, YVO₄, YLF, or YAl₅O₁₂ which is doped with Nd, Tm,or Ho, or a semiconductor laser is preferably used. A fundamental waveof an oscillation wavelength is changed dependent on a doping material.An oscillation is produced at a wavelength of 1 μm to 2 μm. When anon-single crystalline semiconductor film is crystallized, in order toselectively absorb a laser beam by the semiconductor film, it ispreferable that the second harmonic to the fourth harmonic of theoscillation wavelength is applied. Typically, in the case ofcrystallization of amorphous silicon, the second harmonic (532 nm) of anNd:YAG laser (fundamental wave: 1064 nm) is used.

In addition, a gas laser such an argon laser, a krypton laser, or anexcimer laser can be applied.

Also, an atmosphere at laser light irradiation may be an atmospherecontaining oxygen, an atmosphere containing nitrogen, an inertatmosphere, or a vacuum and is preferably selected as appropriateaccording to a purpose.

An oscillation mode may be either pulse oscillation or continuousoscillation. In order to achieve continuous crystal growth with a moltenstate of the semiconductor film, it is desirable that a continuousoscillation mode is selected.

In the case where a TFT which is made from a semiconductor filmcrystallized by laser annealing is formed on a substrate, when a crystalgrowth direction is aligned with a carrier moving direction, high fieldeffect mobility can be obtained. In other words, when the crystal growthdirection is aligned with the channel length direction, the field effectmobility can be substantially increased.

When a continuous oscillating laser beam is irradiated to a non-singlecrystalline semiconductor film for crystallization, a solid-liquidinterface is kept. Thus, a continuous crystal growth can be obtained inthe scanning direction of the laser beam. As shown in FIG. 4, withrespect to a TFT substrate (substrate to which TFTs are mainly formed)112 used for manufacturing an active matrix liquid crystal displaydevice which driver circuits are integrally formed, driver circuitportions 114 and 115 are provided in the vicinity of a pixel portion113. FIG. 4 shows a configuration of a laser irradiation apparatus madein consideration of such a layout. As described above, in the case ofthe configuration in which laser beams are incident from the biaxialdirections, laser beams can be synchronously or asynchronouslyirradiated in an X-direction and a Y-direction indicated by arrows inthe drawing by a combination of the galvanomirrors 104 and 110 and themovable mirrors 105 and 111. In addition, it is possible that a locationis designated according to the layout of TFTs and a laser beam isirradiated thereto.

FIG. 5 shows a relationship between the substrate 112 to which TFTs areprovided and an irradiation direction of a laser beam in detail. Regionsin which the pixel portion 113 and the driver circuits 114 and 115 areformed are indicated by dot lines on the substrate 112. In a stage ofcrystallization, a non-single crystalline semiconductor film is formedon the entire surface. Semiconductor regions for forming TFTs can bedesignated by alignment makers or the like formed in end portions of thesubstrate.

For example, the driver circuit portion 114 is a region for forming ascan line driver circuit. In its partially enlarged view 301,semiconductor regions 204 of TFTs and a scanning direction of a laserbeam 201 are indicated. The semiconductor regions 204 having anarbitrary shape can be applied. In any case, the channel lengthdirection is aligned with the scanning direction of the laser beam 201.In addition, the driver circuit portion 115 extended in a direction inwhich it intersects the driver circuit portion 114 is a region forforming a data line driver circuit, and an arrangement of semiconductorregions 205 is aligned with a scanning direction of a laser beam 202(enlarged view 302). Similarly, in the case of the pixel portion 113, asshown in an enlarged view 303, an arrangement of no semiconductorregions 206 is aligned and a laser beam 202 is scanned in a channellength direction. The scanning direction of the laser beam is notlimited to a single direction and round trip scanning may be conducted.

Next, steps of crystallizing a non-single crystalline semiconductor filmand producing a TFT from the formed crystalline semiconductor film willbe descried with reference to FIGS. 6A to 6D. FIG. 6B is a longitudinalcross sectional view. A non-single crystalline semiconductor film 403 isformed on a glass substrate 401. A typical example of the non-singlecrystalline semiconductor film 403 is an amorphous silicon film. Inaddition, an amorphous silicon germanium film or the like can beapplied. The thickness of 10 nm to 20 nm can be applied and may befurther increased in accordance with a wavelength of a laser beam and anenergy density thereof. In addition, it is desirable to employ such ameasure that a blocking layer 402 is provided between the glasssubstrate 401 and the non-single crystalline semiconductor film 403 soas not to diffuse an impurity such as alkali metal from the glasssubstrate into the semiconductor film. A silicon nitride film, a siliconoxynitride film, or the like is applied as the blocking layer 402.

Also, a laminate 409 of a metallic layer or a metallic nitride layer andan oxide layer is formed between the blocking layer 402 and thesubstrate 401 for peeling. As the metallic layer or the nitride layer,there is preferably used a nitride comprising a single layer made of anelement selected from Ti, Al, Ta, W, Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh,Pd, Os, Ir, and Pt, or an alloy material or a compound material whichcontains the above element as a main ingredient, or a laminate of those.For example, a single layer made of titanium nitride, tungsten nitride,tantalum nitride, or molybdenum nitride, or a laminate of those ispreferably used. Here, a titanium nitride film having a film thicknessof 100 nm which is formed by a sputtering method is used. Note that,when a contact property to the substrate is low, a buffer layer ispreferably provided. A single tungsten layer and a tungsten nitride havea high contact property and are exemplified as preferable materials. Inaddition, as the oxide layer, a single layer made of a silicon oxidematerial or a metallic oxide material, or a laminate of those ispreferably used. Here, a silicon oxide film having a film thickness of200 nm which is formed by a sputtering method is used. Bonding forcebetween the metallic nitride layer and the oxide layer has a sufficientstrength to withstand heat treatment Thus, film peeling (which is alsocalled peeling) or the like is not caused. However, peeling can besimply performed in an inner portion of the oxide layer or a boundarythereof by a physical means. Note that a glass substrate is used here.However, various substrates can be used in the above peeling method. Asthe substrate 401, a quartz substrate, a ceramic substrate, a siliconsubstrate, a metallic substrate, or a stainless steel substrate may beused.

Next, crystallization is conducted by irradiation of a laser beam 400.Thus, a crystalline semiconductor film 404 can be formed. As shown inFIG. 6A, the laser beam 400 is scanned to a position of a semiconductorregion 405 where a TFT will be formed. A beam shape can be set to be anarbitrary shape such as a rectangular shape, a linear shape, or anelliptical shape. With respect to the laser beam condensed by an opticalsystem, an energy intensity at a central region thereof is notnecessarily equal to that at an edge region. Thus, it is desirable thatthe semiconductor region 405 is not overlapped with the edge region ofthe beam.

Scanning of the laser beam is not limited to scanning in only a singledirection and round trip scanning may be conducted. In this case, alaser energy density is changed every time scanning is conducted. Thus,a stepwise crystal growth can be produced. The scanning can also serveas dehydrogenation processing which is often required in the case ofcrystallization of amorphous silicon. For example, first scanning isconducted at a low energy density to release hydrogen, and then secondscanning is conducted at an increased energy density to complete thecrystallization.

When continuous oscillation laser beam irradiation is conducted in sucha laser beam irradiation method, the growth of crystal having a largergrain size is possible. Of course, in order to realize this, it isnecessary to set parameters such as a scanning speed of a laser beam andan energy density thereof in detail as appropriate. When the scanningspeed is set to 10 cm/sec to 80 cm/sec, the above crystal growth can berealized. It is said that a speed of crystal growth throughmelting-solidification using a pulse laser is 1 m/sec. If a laser beamis scanned at a speed lower than the crystal growth speed and slowcooling is conducted, continuous crystal growth in a solid-liquidinterface is possible. Thus, an increase in a grain size of crystal canbe realized.

According to the laser irradiation apparatus of this embodiment, undersuch a situation, it is possible that a position on the substrate isarbitrarily designated and laser beam irradiation is conducted forcrystallization. When laser beam irradiation is conducted from biaxialdirections, a throughput can be further improved.

Also, when laser beam irradiation is conducted, clean peeling from thesubstrate can be performed with smaller force. Thus, a layer to bepeeled that has a large area can be peeled over the entire surfacethereof.

In order to further promote peeling, a granular oxide (for example, ITO(alloy of indium oxide and tin oxide), an alloy of indium oxide and zincoxide (In₂O₃—ZnO), a zinc oxide (ZnO) or the like) may be provided in aninterface between the nitride layer, the metallic layer, or the metallicnitride layer and the oxide layer.

Then, as shown in FIGS. 6C and 6D, the formed crystalline semiconductorfilm is etched to form a semiconductor region 405 in an island-shape. Inthe case of a top gate TFT, a gate insulating film 406, a gate electrode407, and impurity regions 408 having a conductivity type are formed onthe semiconductor region 405 to produce a TFT. Then, wirings, aninterlayer insulating film, and the like are preferably formed asappropriate by a known technique to produce an element.

Thus, after obtaining the element having the TFT, the substrate 401 ispeeled in accordance with the embodiment mode. In this embodiment, aresultant layer formed on the blocking layer 402 corresponds to thelayer to be peeled 11 b which is described in the embodiment mode. Whenthe mechanical strength of the layer to be peeled is insufficient, it ispreferable that the substrate is peeled after a support member (notshown) for fixing the layer to be peeled is bonded thereto.

The layer to be peeled which is formed on the oxide layer can be simplyseparated from the substrate by peeling. The peeled layer can be bent ina certain direction. It is needless to say that the layer to be peeledcan be bonded to a transcriptional body (not shown) having a curvedsurface.

Also in this embodiment, according to the present invention, theirradiation direction (scanning direction) of the laser light and thechannel length directions of all semiconductor layers 204 to 206 and 405provided to the layer to be peeled are set to be the same direction, andthese directions and the bending direction are set to be orthogonal toeach other. Thus, a display having a curved surface can be realized.

Also, this embodiment can be freely combined with the embodiment mode.

Embodiment 2

The example of the top gate TFT is descried in Embodiment 1. Here, anexample of a bottom gate TFT will be described. Also, the structureexcept for the TFT is the same one as Embodiment 1 and the descriptionis thereof omitted here.

Next, steps of crystallizing a non-single crystalline semiconductor filmand producing a TFT from the formed crystalline semiconductor film willbe descried with reference to FIGS. 7A to 7D.

FIG. 7B is a longitudinal cross sectional view. A non-single crystallinesemiconductor film 503 is formed on a gate insulating film 506 coveringa gate electrode. A typical example of the non-single crystallinesemiconductor film 503 is an amorphous silicon film. In addition, anamorphous silicon germanium film or the like can be applied. Thethickness of 10 nm to 200 nm can be applied and may be further increasedin accordance with a wavelength of a laser beam and an energy densitythereof. In addition, it is desirable to employ such a measure that ablocking layer 502 is provided between the glass substrate 501 and thegate electrode so as not to diffuse an impurity such as alkali metalfrom the glass substrate into the semiconductor film. A silicon nitridefilm, a silicon oxynitride film, or the like is applied as the blockinglayer 502.

Also, a laminate 509 of a metallic layer or a metallic nitride layer andan oxide layer is formed between the blocking layer 502 and thesubstrate 501 for peeling. As the metallic layer or the nitride layer,there is preferably used a nitride comprising a single layer made of anelement selected from Ti, Al, Ta, W, Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh,Pd, Os, Ir, and Pt, or an alloy material or a compound material whichcontains the above element as a main ingredient, or a laminate of thoseis preferably used. For example, a single layer made of titaniumnitride, tungsten nitride, tantalum nitride, or molybdenum nitride, or alaminate of those is preferably used. Here, a titanium nitride filmhaving a film thickness of 100 nm which is formed by a sputtering methodis used. Note that, when a contact property to the substrate is low, abuffer layer is preferably provided. A single tungsten layer and atungsten nitride have a high contact property and are exemplified aspreferable materials. In addition, as the oxide layer, a single layermade of a silicon oxide material or a metallic oxide material, or alaminate of those is preferably used. Here, a silicon oxide film havinga film thickness of 200 nm which is formed by a sputtering method isused. Bonding force between the metallic nitride layer and the oxidelayer has a strength resistant to heat treatment. Thus, film peeling(which is also called peeling) or the like is not caused. However,peeling can be simply performed in an inner portion of the oxide layeror a boundary thereof by a physical means.

Next, crystallization is conducted by irradiation of a laser beam 500.Thus, a crystalline semiconductor film 504 can be formed. The laser beamis obtained from the laser processing apparatus described inEmbodiment 1. As shown in FIG. 7A, the laser beam 500 is scanned to aposition of a semiconductor region 505 where a TFT will be formed. Abeam shape can be set to be an arbitrary shape such as a rectangularshape, a linear shape, or an elliptical shape. With respect to the laserbeam condensed by an optical system, an energy intensity at a centralregion thereof is not necessarily equal to that at an edge region. Thus,it is desirable that the semiconductor region 505 is not overlapped withthe edge region of the beam.

Scanning of the laser beam is not limited to scanning in only a singledirection and round trip scanning may be conducted. In this case, alaser energy density is changed every time scanning is conducted. Thus,a stepwise crystal growth can be produced. The scanning can also serveas dehydrogenation processing which is often required in the case ofcrystallization of amorphous silicon. For example, first scanning isconducted at a low energy density to release hydrogen, and then secondscanning is conducted at an increased energy density to complete thecrystallization.

When continuous oscillation laser beam irradiation is conducted in sucha laser beam irradiation method, the growth of crystal having a largergrain size is possible. Of course, in order to realize this, it isnecessary to set parameters such as a scanning speed of a laser beam andan energy density thereof in detail as appropriate. When the scanningspeed is set to 10 cm/sec to 80 cm/sec, the above crystal growth can berealized. It is said that a speed of crystal growth throughmelting-solidification using a pulse laser is 1 m/sec. If a laser beamis scanned at a speed lower than the crystal growth speed and slowcooling is conducted, continuous crystal growth in a solid-liquidinterface is possible. Thus, an increase in a grain size of crystal canbe realized.

Also, when laser beam irradiation is conducted, clean peeling from thesubstrate can be performed with smaller force. Thus, a layer to bepeeled that has a large area can be peeled over the entire surfacethereof.

In order to further promote peeling, a granular oxide (for example, ITO(alloy of indium oxide and tin oxide), an alloy of indium oxide and zincoxide (In₂O₃—ZnO), a zinc oxide (ZnO) or the like) may be provided in aninterface between the nitride layer, the metallic layer, or the metallicnitride layer and the oxide layer.

Then, as shown in FIGS. 7C and 7D, the formed crystalline semiconductorfilm is etched to form a semiconductor region 505 in an island-shape.Here, an etching stopper is provided on a semiconductor region 505, andimpurity regions 508 having one conductivity type are formed to producea TFT. Then, wirings, an interlayer insulating film, and the like arepreferably formed as appropriate by a known technique to produce anelement.

Thus, after obtaining the element having the TFT, the substrate 501 ispeeled in accordance with the embodiment mode. In this embodiment, aresultant layer formed on the blocking layer 502 corresponds to thelayer to be peeled 11 b which is described in the embodiment mode. Whenthe mechanical strength of the layer to be peeled is insufficient, it ispreferable that the substrate is peeled after a support member (notshown) for fixing the layer to be peeled is bonded thereto.

The layer to be peeled which is formed on the oxide layer can be simplyseparated from the substrate by peeling. The peeled layer can be bent ina certain direction. It is needless to say that the layer to be peeledcan be bonded to a transfer body (not shown) having a curved surface.

Even in this embodiment, the irradiation direction (scanning direction)of the laser light and the channel length directions of thesemiconductor layer 505 provided to the layer to be peeled are set to bethe same direction, and these directions and the bending direction areset to be orthogonal to each other. Thus, a display having a curvedsurface can be realized.

Also, this embodiment can be freely combined with the embodiment mode.

Embodiment 3

In accordance with the present embodiment, FIG. 8 shows a technique fortransferring a layer to be peeled containing TFT.

In FIGS. 8A to 8G, reference numeral 830 indicates a first substrate;reference numeral 831 indicates a first material layer composed of anitride layer or a metallic layer; reference numeral 832 indicates asecond material layer composed of an oxide layer; reference numeral 833indicates a layer to be peeled; reference numeral 834 indicates a firstadhesive; reference numeral 835 indicates a second substrate; referencenumeral 836 indicates a second adhesive; and reference numeral 837indicates a third substrate.

In accordance with the present embodiment, the first substrate 830 maybe constituted by a glass substrate, a quartz substrate, a ceramicsubstrate or the like. Further, it is also possible to use asemiconductor substrate such as a silicon substrate, or a metallicsubstrate such as a stainless steel substrate. Here, a glass substrate(#1737) having a thickness of 0.7 mm is used.

First, as shown in FIG. 8A, on top of the substrate 830, the firstmaterial layer 831 is formed. The first material layer 831 may be amaterial which, immediately after the film is formed, exhibits one ofcompression stress and tension stress. However, it is important to use amaterial in which abnormalities such as peeling due to thermalprocessing and laser light radiation, in the forming of the layer to bepeeled, do not occur, and which exhibits tension stress in a range of 1to 1×10¹⁰ (Dyne/cm²) after the forming of the layer to be peeled. Arepresentative example is a single layer constituted by an elementselected from the group consisting of W, WN, TiN, and TiW, or by analloy metal or compound material having the element as its maincomponent, or a laminate thereof. Note that, the first material layer831 may be formed using a sputtering method.

Next, the second material layer 832 is formed on top of the firstmaterial layer 831. In the second material layer 832, it is important touse a material in which abnormalities such as peeling caused by thethermal processing and the laser light radiation, in the forming of thelayer to be peeled, do not occur, and which exhibits compression stressin a range of 1 to 1×10¹⁰ (Dyne/cm²) after the forming of the layer tobe peeled. Representative examples of the second material layer includeoxide silicon, oxide silicon nitride, oxide metallic material, and alaminate of these. Note that, the second material layer 832 may beformed using a sputtering method. In the case where the second materiallayer 832 is formed using the sputtering method, an inert gas such asargon gas is introduced into the chamber, to include a minute amount ofArgon gas elements into the second material layer 832.

Regarding the first material layer 831 and the second material layer832, the film widths of each of the layers is set as needed within arange of 1 nm to 1000 nm, to thereby adjust the internal stress of thefirst material layer 831 and the internal stress of the second materiallayer 832.

Further, in FIGS. 8A to 8G, in order to streamline the process, anexample has been shown in which the first material layer 831 is formedin contact with the substrate 830. However, an insulating layer ormetallic layer serving as a buffer may be provided in between thesubstrate 830 and the first material layer 831 to improve the adhesionwith the substrate 830.

Next, the layer to be peeled is formed onto the second material layer832. (See FIG. 8A). The layer to be peeled 833 may contain variouselements (e.g., a film transistor, light emitting elements in which alayer containing organic compounds serves as a light emitting layer,elements containing liquid crystals, a memory element, a thin-filmdiode, a photoelectric conversion element formed by a silicon pinjunction, or a silicon resistor element). However, in the case ofelements containing liquid crystals, the layer to be peeled 833 mustinclude a substrate which opposes it. Further, the process of formingthe layer to be peeled 833 can be accomplished by thermal processingconducted within the temperature range that the first substrate 830 canwithstand. Note that, even if the internal stress in the second materiallayer 832 and the internal stress in the first material layer 831 aredifferent than each other, the thermal processing in the manufacturingof the layer to be peeled 833 will not cause peeling to occur.

Next, a process is performed for partially reducing the adhesion betweenthe first material layer 831 and the second material layer 832. Theprocessing for partially reducing the adhesion is a process in which alaser light is partially radiated on the first material layer or on thesecond material layer along the perimeter of the region to be peeled, oris a process in which localized pressure is applied from the outsidealong the perimeter of the region to be peeled to apply damage to a partof the inside or the surface of the second material layer. Specifically,a diamond or other such hard needle may be pressed perpendicularly andmoved while applying pressure. Preferably, a scriber device is used andis pressed down by an amount of 0.1 mm to 2 mm, with pressure beingapplied as it is moved. In this way, before performing the peeling, itis important to create a portion where peeling can occur easily, whichserves as a starter. By performing the preprocessing in which theselective (partial) reduction of the adhesion takes place, defectivepeelings are eliminated and yield is improved.

Next, the second substrate 835 and the layer to be peeled 833 areadhered to each other using the first adhesive 834. (See FIG. 8B). Thefirst adhesive 834 may be a reactive-curing type adhesive, athermal-curing type adhesive, an ultraviolet-curing type adhesive orother such photo-curing type adhesive, or may be an aerophobic-typeadhesive, or other various types of curing adhesive. Moreover, theseadhesives may be soluble such that they dissolve in a solvent, and/ormay be photosensitive such that their adhesiveness decreases whenirradiated with light. The composition of these adhesives may be, forexample, epoxy-type, acrylic-type, silicon-type or anything else. Theapplication of the adhesive may be carried out by a coating method, forexample. Note that, the first adhesive is removed in subsequent steps.Here, a soluble adhesive material which can dissolve in a solvent isused as the fist adhesive.

Further, instead of the first adhesive 834, a tape having adhesive onone or both of its surfaces may be used. The tape may include on one orboth of its surfaces an adhesive which is soluble so as to dissolve in asolvent, or is photosensitive so as to lose adhesiveness when irradiatedwith light.

The second substrate 835 may be constituted by a glass substrate, aquartz substrate, a ceramic substrate, a plastic substrate or the like.Further, it is also possible to use a semiconductor substrate such as asilicon substrate, or a metallic substrate such as a stainless steelsubstrate.

The present embodiment employs a highly rigid quartz substrate(thickness: 1.1 mm) for the second substrate 835, having a thicknesslarger than the first substrate 830. In the case where a plastic film isused for the second substrate, when the elements formed onto the firstsubstrate 830 are transferred onto the plastic film—which is to say whenthe layer to be peeled 833 and the film are adhered to each other by thefirst adhesive 834 and the film is lifted up—there was a risk that thefilm will bend and cause cracks to form in the layer to be peeled 833.Therefore, after fixing the layer to be peeled 833 formed over the firstsubstrate 830 to the rigid second substrate 835 with the first adhesive834, the first substrate 830 is peeled. Then, after the plastic film(i.e., the third substrate 837) is fixed to the layer with the secondadhesive 836, the second substrate 835 is removed. By following thisprocedure, it becomes difficult for cracks to occur.

Next, peeling is performed from the above-mentioned region where theadhesiveness has been reduced, and the first substrate 830 having thefirst material layer 831 is separated by using a physical means (FIG.8C). Since the second material layer 832 exhibits compressional stressand the first material has tension stress, the separation can beachieved with relatively little force (such as the force of a humanhand, or wind pressure of gas blown from a nozzle, or ultrasonic waves,etc.).

Thus, the layer to be peeled 833 formed onto the second material layer832 can be separated from the first material layer 830. FIG. 8D showsthe post-peeled state.

Next, the third substrate 837 and the second material layer 832 (and thepeeled layer 833) are adhered together with the second adhesive 836.(See FIG. 8E). It is important that the second adhesive 836 has greateradhesive force than the first adhesive 834.

The second adhesive 836 may be a reactive-curing type adhesive, athermal-curing type adhesive, an ultraviolet-curing type adhesive orother such photo-curing type adhesive, or may be an aerophobic-typeadhesive, or other various types of curing adhesive. Moreover, theseadhesives may be soluble such that they dissolve in a solvent, and/ormay be photosensitive such that their adhesiveness decreases whenirradiated with light. The composition of these adhesives may be, forexample, epoxy-type, acrylic-type, silicon-type or anything else. Theapplication of the adhesive may be carried out by a coating method, forexample. Note that, the second adhesive becomes one support for thelayer to be peeled at a subsequent step. For the second adhesive 836, amaterial is used which will achieve a high degree of adhesion betweenthe third substrate and the second adhesive, and also between the secondadhesive and the layer to be peeled. Here, an ultraviolet-curing typeadhesive is used for the second adhesive 836.

Further, in the case where the second adhesive 836 is made of a materialwhich is soluble so as to dissolve in a solvent, or is photosensitivesuch that it loses adhesive strength when exposed to light, it becomespossible to peel the third substrate at a later step, and it is possiblefor only the second adhesive to serve as the support. Further, insteadof the second adhesive 836, it is possible to use a tape having adhesiveon one or both of its surfaces. The surface or surfaces of this tape mayhave an adhesive which is soluble so as to dissolve in a solvent, orphotosensitive such that its adhesive strength decreases when the tapeis exposed to light.

A flexible substrate may be used for the third substrate 837. Thepresent embodiment employs a plastic film for the third substrate 837.

Once the situation shown in FIG. 8E is achieved, it is then soaked inthe solvent and only the second substrate 835 is removed. (See FIG. 8F).Since the first adhesive is a soluble adhesive material, the secondsubstrate 835 is removed easily, thus separating the second substrate835 and the layer to be peeled 833.

Further, an input/output terminal of the element contained in the layerto be peeled 833 is formed so as to be exposed from the topmost layer(i.e., the layer closest to the second substrate side) of the layer tobe peeled. Therefore, after the step of separating the second substrate,it is preferable that the first adhesive is completely removed from thesurface of the layer to be peeled so that the input/output terminalportion can be exposed.

Further, in the present embodiment, there is shown the example in whichthe soluble adhesive material is used for the first adhesive 834 suchthat it dissolves in a solvent and in which the second substrate issoaked in the solvent and removed. However, the invention is notparticularly restricted to this configuration. For example, athermal-curing type adhesive (which loses adhesive strength whenirradiated with ultraviolet light) may be used for the first adhesive,and ultraviolet rays may be radiated to thereby remove the secondsubstrate.

The steps described above enable the manufacture of a semiconductordevice equipped with the layer to be peeled 833 which serves as asupport for the second adhesive 836 and the third substrate 837. Then,by curving the device as shown in FIG. 8G, it thus becomes possible toachieve a semiconductor device in which the curved surface of thesemiconductor device exhibits a radius of curvature of from 50 cm to 200cm. When curving the device, it can be attached to the curved surface towhich it is going to be mounted. Note that, between the second adhesive836 and the layer to be peeled 833, there is the oxide layer 832 that isthe second material layer. In the semiconductor device obtained asdescribed above, the second material layer 832 is applied by asputtering method and minute amounts of inert gas elements are includedin the second material layer 832. Therefore, the semiconductor device asa whole can be made flexible.

Further, in accordance with the present embodiment, the device wascurved after being attached to the third substrate. However, it is alsopossible to curve the device by attaching it directly to a base that hasa curved surface, with the second adhesive 836.

Here, an example was shown in which the semiconductor device is built tocompletion according to the steps described above, but it is alsopossible to follow the above-mentioned steps to complete thesemiconductor device only partially. For example, according to theabove-mentioned steps, it is possible to form the layer to be peeledcontaining a TFT circuits, and then, after obtaining the layer to bepeeled which has as a support therefor the second adhesive and the thirdsubstrate, steps of forming elements may be added to complete any of avariety of semiconductor devices, such as a light emitting device or aliquid crystal display device having a light emitting elements in whicha layer containing an organic compound serves as a light emitting layer.

Further, it is also possible to make a light emitting device having alight emitting element in which a layer containing a passive organicelement compound serves as a light emitting layer.

Further, in a case where, in order to reduce the adhesion between thethird substrate and the second adhesive, a plastic film in which anAlN_(X)O_(Y) film is formed on the surface is formed as the thirdsubstrate 837, it becomes possible to separate the second substrate 835and the third substrate 837. It thus becomes possible to manufacture asemiconductor device equipped with the layer 833 to be peeled having thesecond adhesive 836 as a support. Since such a semiconductor device hasonly the second adhesive as a support, it can be made thin, lightweightand flexible.

Further, by following the above-mentioned steps, the present inventorsactually performed electrical measurement of the TFT formed onto thefirst substrate before peeling the first substrate, and after separatingthe first and the second substrate, they performed the electricalmeasurement of the TFT once again. There was hardly any change in thecharacteristics of the TFT before and after separation. FIG. 9 is a V-Icharacteristic graph for an n-channel type TFT with the post-separationchannel length L/channel width W=50 μm/50 μm. Further, FIG. 10 is a V-Icharacteristic graph for a p-channel type TFT with the post-separationchannel length L/channel width W=50 μm/50 μm.

Since there was hardly any change in the characteristics of the TFTbefore and after the separation, it can be said that, even when thetransferring and application are performed according to the sequencedescribed above, the above-mentioned steps do not affect the TFTs.Further, it is also possible to directly form the TFT onto the plasticsubstrate; however, since the substrate's heat resistance is low, itwould be difficult to perform thermal processing at 300° C. or higher.Thus, it would be difficult to form the TFT with the excellentcharacteristics shown in FIG. 9 and FIG. 10. As demonstrated in thepresent embodiment, after the TFT is formed onto the heat-resistantsubstrate, the heat-resistant substrate is then peeled. Accordingly, itthus becomes possible to form the TFT exhibiting the excellentcharacteristics as shown in FIG. 9 and FIG. 10.

Embodiment 4

In this embodiment, in accordance with the technology described inEmbodiment 3, manufacturing steps of a light emitting device having alight emitting element in which a layer having an organic compoundserves as a light emitting layer will be described with reference toFIG. 11.

First, pixel portions (n-channel TFTs and p-channel TFTs) and drivercircuits (n-channel TFTs and p-channel TFTs) provided in the vicinity ofthe pixel portions are manufactured simultaneously on one substrate,organic light emitting elements (also called organic light emittingdevice) are formed thereon.

A first material layer 931 made of nitride layer or a metal layer and asecond material layer 932 made of an oxide layer are formed on a firstsubstrate in accordance with Embodiment 3.

Next, a layer containing TFTs and wirings is formed on the secondmaterial layer 932 in accordance with the technology shown inEmbodiment 1. After an insulation film for covering respective TFT isformed, a cathode or an anode electrically connected with TFTs providedin the pixel portion is formed. Further, an insulator called bank isformed to cover the ends of the cathode or the anode on both endsthereof. Moreover, if necessary, it is practicable to form a passivationfilm (protection film) to cover TFTs optionally. And, an EL layer(organic compound material layer) and the anode or the cathode oforganic light emitting elements are formed on the cathode or the anodeboth ends of which are covered by bank. When the under layer of the ELlayer is a cathode, an anode can be provided on the EL layer, on thecontrary, when the under layer of the EL layer is an anode, a cathodecan be provided on the EL layer.

As the EL layer, an EL layer (layer for light emitting and makingcarrier perform the migrate for it) may be formed by freely combiningthe light emitting layer, a charge injection layer or a chargeimplantation layer. For example, low molecular system organic ELmaterial and high molecular system organic EL material may be employed.Moreover, as an EL layer, a thin film out of a light emitting material(singlet compound) which light-emits (fluorescence) due to singletexcitation, or a thin film out of a light emitting material (tripletcompound) which emits (phosphorescence) due to triplet excitation can beused. Moreover, an inorganic material such as silicon carbide or thelike is capable of being used as a charge transport layer and a chargeinjection layer. For these organic EL material and inorganic material,the known materials can be used. In addition, the EL layer is totallyformed in a thickness around 100 nm as a thin film layer. For thisreason, it is necessary to enhance the evenness of the surface of thecathode or the anode.

As a material used for a cathode, it is said that it is preferable touse a metal having a small work function (representatively, metalelements belonging to I group or II group of the periodic table) or analloy containing these. Since the smaller the work function is, the morethe luminous efficiency is enhanced, it is preferable that among these,as a material used for a cathode, an alloy containing Li (lithium),which is one of alkaline metals, is used.

As a conductive film using for the anode, a material having a biggerworking function in comparison with the material of the cathode such asITO (indium oxide-tin oxide alloy), indium oxide-zinc oxide alloy(In₂O₃—ZnO), zinc oxide (ZnO) or the like may be used. Further, amaterial having a lower sheet resistance than ITO, specifically,platinum (Pt), chromium (Cr), tungsten (W), or nickel (Ni) may be used.

An organic light emitting layer is defined in this specification as anaggregate of layers formed between an anode and cathode of a lightemitting element in which a layer containing an organic compound servesas a light emitting layer. Specifically, an organic light emitting layerincludes a light emitting layer, a hole injecting layer, an electroninjecting layer, a hole transporting layer, an electron transportinglayer, etc. The basic structure of an organic light emitting element isa laminate of an anode, a light emitting layer, and a cathode layered inorder. The basic structure may be modified into a laminate of an anode,a hole injecting layer, a light emitting layer, and a cathode layered inorder, or a laminate of an anode, a hole injecting layer, a lightemitting layer, an electron transporting layer, and a cathode layered inorder.

A light emitting element in which a layer containing an organic compoundserves as a light emitting layer has, in addition to an anode and acathode, a layer containing an organic compound (light emittingmaterial) that generates luminescence (electro luminescence) when anelectric field is applied (the layer is hereinafter referred to a lightemitting layer).

When a current flowing to the light emitting element is controlled byTFTs, there are two methods in a rough dividing way. Specifically, onemethod is controlling the current in a voltage region called saturationregion, the other is controlling the current in a voltage region beforereaching the saturation region. In this specification, a Vd region wherea current value is substantial constant is referred to as a saturationregion in Vd-Id curve. In addition, in the invention, there is nolimitation putted on the driving methods of the light emitting element,that is to say, any driving methods can be used.

By the steps up through this point, the layer to be peeled is formed bylaminating a layer 933 b containing the light emitting element in whicha layer containing an organic compound serves as a light emitting layer,and a layer 933 a having TFTs and connected to the light emittingelement. Since the light emitting element in which a layer containing anorganic compound serves as a light emitting layer is weak againstmoisture and oxygen, immediately after the light emitting element inwhich a layer containing an organic compound serves as a light emittinglayer is formed, using a substrate, a sealing can, and a sealant to sealit.

Next, a process is performed for partially reducing the adhesion betweena first material layer 931 and a second material layer 932. Theprocessing for partially reducing the adhesion is a process in which alaser light is partially radiated on the first material layer or on thesecond material layer along the perimeter of the region to be peeled, oris a process in which localized pressure is applied from the outsidealong the perimeter of the region to be peeled to apply damage to a partof the inside or the surface of the second material layer. Specifically,a diamond or other such hard needle may be pressed perpendicularly andmoved while applying pressure. Preferably, a scriber device is used andis pressed down by an amount of 0.1 mm to 2 mm, with pressure beingapplied as it is moved. In this way, before performing the peeling, itis important to create a portion where peeling can occur easily, whichserves as a starter. By performing the preprocessing in which theselective (partial) reduction of the adhesion takes place, defectivepeelings are eliminated and yield is improved.

Subsequently, a FPC 901 is attached to a terminal electrode provided atthe end of an outgoing wiring to which TFT provided on the layer to bepeeled 933 is connected.

Next, a second substrate 935 and the layers to be peeled 933 a, 933 bare adhered to each other using a first adhesive 934. (See FIG. 11B) Afilm 902 is adhered to the second substrate 935 with an adhesive 903 inadvance. The adhesive 903 is desired to be weaker in adhesive force thanthat of the first adhesive 934, and it is also desired to be an adhesivewhich is soluble so as to dissolve in a solvent, or is photosensitive soas to lose adhesiveness when irradiated with light. However, theadhesive 903 is removed in subsequent steps. Further, instead of thefirst adhesive 934, a tape having adhesive on one or both of itssurfaces may be used. The tape may include on one or both of itssurfaces an adhesive which is soluble so as to dissolve in a solvent, oris photosensitive so as to lose adhesiveness when irradiated with light.

The first adhesive 934 may be a reactive-curing type adhesive, athermal-curing type adhesive, an ultraviolet-curing type adhesive orother such photo-curing type adhesive, or may be an aerophobic-typeadhesive, or other various types of curing adhesive. The composition ofthese adhesives may be, for example, epoxy-type, acrylic-type,silicon-type or anything else. However, since a light emitting elementin which a layer containing an organic compound serves as a lightemitting layer is weak against moisture and oxygen, a material with highbarrier to moisture and oxygen is preferable. The application of suchadhesives may be carried out by a coating method, for example. In thisembodiment, for the first adhesive 934, used is a thermal-curing typeadhesive.

The second substrate 935 may be constituted by a glass substrate, aquartz substrate, a ceramic substrate, a plastic substrate or the like.Further, it is also possible to use a semiconductor substrate such as asilicon substrate, or a metallic substrate such as a stainless steelsubstrate.

The present embodiment employs a highly rigid quartz substrate(thickness: 1.1 mm) for the second substrate 935, having a thicknesslarger than that of the first substrate 930. In the case where a plasticfilm is used for the second substrate, when the elements formed onto thefirst substrate 930 are transferred onto the plastic film—which is tosay when the layer to be peeled 933 and the film are adhered to eachother by the first adhesive 934 and the film is lifted up—there was arisk that the film will bend and cause cracks to form in the layer to bepeeled 933. Therefore, after fixing the layer to be peeled 933 formedover the first substrate 930 to the rigid second substrate 935 with thefirst adhesive 934, the first substrate 930 is peeled. Then, after theplastic film (i.e., the third substrate 937) is fixed to the layer withthe second adhesive 936, the second substrate 935 is removed. Byfollowing this procedure, it becomes difficult for cracks to occur.

Next, peeling is performed from the above-mentioned region where theadhesiveness has been reduced, and the first substrate 930 having thefirst material layer 931 is separated by using a physical means. (SeeFIG. 11C) Since the second material layer 932 exhibits compressionalstress and the first material has tension stress, the separation can beachieved with relatively little force (such as the force of a humanhand, or wind pressure of gas blown from a nozzle, or ultrasonic waves,etc.).

It thus becomes possible to separate the layers to be peeled 933 a and933 b formed on the second material layer 932 from the first substrate930.

Subsequently, the third substrate 937 and the second material layer 932(and layers to be peeled 933 a, 933 b) are bonded together by the secondadhesive 936 (FIG. 11D). It is essential that the adhesive 936 hasgreater adhesive force than that of the adhesive 903.

The second adhesive 936 may be a reactive-curing type adhesive, athermal-curing type adhesive, an ultraviolet-curing type adhesive orother such photo-curing type adhesive, or may be an aerophobic-typeadhesive, or other various types of curing adhesive. In this embodiment,for the second adhesive 936, used is a thermal-curing type adhesive.Further, in the case where the second adhesive 936 is made of a materialwhich is soluble so as to dissolve in a solvent, or is photosensitivesuch that it loses adhesive strength when exposed to light, it becomespossible to peel the third substrate at a later step, and it is possiblefor only the film 902, the first adhesive and the second adhesive toserve as the supports.

A flexible substrate can be used for the third substrate 937. In thisembodiment, the plastic film used for 902 also is used for the thirdsubstrate 937.

After the state shown in FIG. 11D is obtained, the adhesive 903 isirradiated by ultraviolet so that the adhesive force is weaken,therefore, only the second substrate 935 is separated (FIG. 11E). Thesecond substrate 935 is easily peeled by irradiating ultraviolet, thesecond substrate 935 and the film 902 are separated thereby.

The steps described above enable the manufacture of a semiconductordevice equipped with the layers to be peeled 933 a, 933 b which servesas a support for the second adhesive 936 and the third substrate 937.Then, by curving the device as shown in FIG. 11F, it thus becomespossible to achieve a semiconductor device in which the curved surfaceof the semiconductor device exhibits a radius of curvature of from 50 cmto 200 cm. When curving the device, it can be attached to the curvedsurface to which it is going to be mounted. Note that, between thesecond adhesive 936 and the layer to be peeled 933 a, there is the oxidelayer 932 that is the second material layer. In the semiconductor deviceobtained as described above, the second material layer 932 is applied bya sputtering method and minute amounts of inert gas elements areincluded in the second material layer 932. Therefore, the semiconductordevice as a whole can be made flexible.

External views of a bent semiconductor device having a light emittingelement in which a layer containing an organic compound serves as alight emitting layer obtained by above steps are shown in FIGS. 12A and12B.

FIG. 12A and FIG. 12B respond to FIG. 1, the same reference symbols areused for the same portions. A semiconductor shown in FIG. 12A emitslight in a direction of an arrow indicated in FIG. 12A, and the deviceis bent in a bending direction 19. Although not illustrated here, allchannel length directions of a large number of semiconductor layersprovided on a pixel portion 12 and a driver circuit 17 are aligned withthe same direction. In addition, assume that the laser light irradiationdirection, that is, a scanning direction is the same direction as thechannel length directions. Thus, when the crystal growth direction isaligned with the channel length direction, the field effect mobility canbe substantially increased.

Further, a semiconductor device shown in FIG. 12B emits light in anopposite direction to the one shown in FIG. 12A, and the device is bentin a bending direction 19. Note that the emitting direction can bedefined at operator's discretion in accordance with manufacturingmethods of a light emitting element in which a layer containing anorganic compound serves as a light emitting layer and compositions ofpixel circuits.

Embodiment 5

The present embodiment illustrates an example in which a display havingthe curved surface obtained by the technique presented in any one ofEmbodiments 1 through 4 is mounted in a vehicle. Here, an automobile isused as a representative example of a vehicle, but restriction is notmade to an automobile. Rather, it goes without saying that the inventionmay be applied in an aircraft, a train, an electric train, or the like.

FIG. 13 is a diagram showing the vicinity around a driver's seat in anautomobile. A dashboard portion is provided with sound playback systems,specifically including a car audio system and a navigating system. Amain unit 2701 of the car audio system includes a display portion 2702and operating switches 2703 and 2704. By executing the present inventionin the display portion 2702, a thin and lightweight car audio system canbe achieved. Further, by executing the present invention in the carnavigation system, a thin and lightweight car navigation system can beachieved.

Further, near a steering wheel portion 2602, the dashboard portion 2601is formed with a display portion 2603 in which digital displays of aspeedometer and other such measuring instruments are made. By executingthe present invention in the display portion 2702, thin and lightweightmechanical display instruments can be achieved.

Further, it is also possible to form a display portion 2602 attachedonto the dashboard 2601 having a curved surface. By executing thepresent invention in the display portion 2602, a thin and lightweightmechanical display instrument or image display device can be achieved.Note that the display portion 2602 is curved in the direction shown bythe arrows.

Further, it is also possible to form a display portion 2600 onto thefront windshield 2604 that has a curved surface. In the case where thepresent invention is adapted for the display portion 2600, a permeablematerial may be used, so that a thin and lightweight mechanical displayinstrument or image display device can be achieved by means of thepresent invention. Note that, the display portion 2600 is curved in thedirection shown by the arrows. Here, the display portion 2600 wasapplied in on the windshield, but it may also be provided to otherwindow glass areas.

It is also possible to form the display portion 2902 attached onto arear window 2900, for example. FIG. 14 is a diagram showing the vicinitysurrounding rear seats in the automobile. Note that, FIG. 14 and FIG. 13correspond to each other, and since the steering wheel portions areidentical, the same reference numerals has been used as in FIG. 13.

Further, by applying a flexible display device according to the presentinvention onto the rear window 2900 and mounting onto the exterior ofthe car a camera which can capture the area behind the car, and then byconnecting the display device and the camera, the driver can see placeswhich are obstructed by the car and could not be seen otherwise. Notethat, the display portion 2902 is curved in the direction shown by thearrows.

Further, if the automobile is driven from the right side as shown inFIG. 14, there is a blind spot on the rear-left side since there is aportion of the vehicle body 2906 there (i.e., the part between windows).However, by applying a flexible display device (display portion 2901)according to the present invention onto the part between the windows andmounting onto the exterior of the car a camera which can capture theblind spot, and by connecting the display device and the camera, thedriver can check the blind spot. Note that, the display portion 2901 iscurved in the direction shown by the arrows.

Further, it is also possible to provide a display portion 2905 onto aseat 2904. A person sitting in the rear seat can watch television andview the display of the car navigational system.

Further, although it is not shown in the diagrams, the ceiling of thecar may serve as a base, and a display device having a light emittingelement in which a layer containing an organic compound serves as alight emitting layer is curved along the curved surface of the ceilingand is attached thereto, whereby image display and illumination insidethe vehicle can be performed.

As described above, the display having the curved surface according tothe present invention can be mounted easily onto any curved surface inthe vehicle having a radius of curvature of 50 cm to 200 cm.

Further, the present embodiment illustrated an on-board car audio systemand car navigating system, but the present invention may be used onother vehicle display instruments and on free-standing audio andnavigational systems.

Further, the present embodiment may be combined freely with any one ofEmbodiments 1 through 4.

Embodiment 6

In Embodiments 1 through 5, the peeling method utilized the film stress(stress deformation) between the two layers to perform the peeling, butrestriction is not made to this method. It is possible to use a methodin which a separation layer is formed between the layer to be peeled andthe substrate, and an etchant is used to separate the separation layerand the substrate, and also a method in which a layer constituted of aamorphous silicon (or a polysilicon) is provided between the layer to bepeeled and the substrate, and a laser light is radiated through thesubstrate to drive out hydrogen contained in the amorphous silicon,thereby creating gaps so as to make the layer to be peeled and thesubstrate separate, for example.

Here, FIGS. 15A to 15D show an example in which the amorphous silicon(or the polysilicon) containing a large amount of hydrogen as itsseparating layer is used and laser light is irradiated onto theseparation layer to perform the peeling.

In FIG. 15A, reference numeral 600 indicates a substrate, referencenumeral 601 indicates a separation layer, and reference numeral 602indicates an layer to be peeled.

In FIG. 15A, a translucent substrate such as a glass substrate or aquartz substrate or the like is used for the substrate 600.

Then, the separation layer 601 is formed. Amorphous silicon orpolysilicon is used for the separation layer 601. Note that, asputtering method or a plasma CVD method, or other film applicationmethods may be used as the separation layer 601 so as to put a largeamount of hydrogen into it as needed.

Next, the layer to be peeled 602 is formed onto the separation layer601. (See FIG. 15A). The layer to be peeled 602 may contain variouselements, of which a TFT is a typical example (others include thin filmdiodes, and photoelectric conversion elements and silicon resistantelements made with silicon PIN-junctions). Further, thermal processingmay be performed within the temperature range that the substrate 600 canwithstand. However, the separation layer 601 is handled in such a waythat peeling off of the film and other problems potentially caused bythe thermal processing in the manufacturing of the layer to be peeled602 do not occur. In the case such as the present embodiment where thelaser light is used to perform the peeling, in order that the hydrogendoes not escape before the peeling is performed, it is desirable thatthe thermal processing temperature is set at 410° C. or below whenforming the elements included in the layer to be peeled.

Next, laser light is irradiated through the substrate 600 onto theseparation layer. (See FIG. 15B). For the laser light, it is possible touse an excimer laser or other such gas laser, a YAG laser or other suchsolid-state laser, or a semiconductor laser. Further, the oscillation ofthe laser light may be continuous oscillation or pulse oscillation, andthe shape of the laser beam may be linear or rectangular. In the presentembodiment, the laser radiation device indicated in Embodiment 1 isused. By using the laser radiation device indicated in Embodiment 1, itis possible to radiate the laser beam across the entirety of a largesurface area with good throughput. Further, the laser radiation deviceindicated in Embodiment 1 can be used not only for crystallizing orpeeling, but also for performing various laser annealing.

When the above-mentioned laser light causes the release of the hydrogencontained in the separation layer 601, gaps are created and the layer tobe peeled 602 and the substrate 600 separate from each other. (FIG.15C). By using the laser radiation device indicated in Embodiment 1, itbecomes possible to peel a layer to be peeled having a large area,across the entire surface thereof with good yield.

The post-peeling state is shown in FIG. 15D. Further, the example shownhere assumes that the mechanical strength of the layer to be peeled 602is sufficient. However, in the case where the mechanical strength of thelayer to be peeled 602 is insufficient, the peeling should be performedafter applying a support (not shown in the diagram) for anchoring thelayer to be peeled 602.

Further, the peeled layer after peeling can be curved in a certaindirection. It also goes without saying that the peeled layer can beapplied and transferred onto an object having a curved surface.

In the present embodiment as well, the direction of the laser lightradiation (i.e., scan direction) and the directions of the channellength of all the semiconductor layers provided to the layer to bepeeled are facing in the same direction, and this direction is madeperpendicular to the direction of the curvature. Accordingly, thedisplay having the curved surface can be realized.

Further, the configuration of the present embodiment may be combinedfreely with Embodiments 1 through 5.

Note that, in the case where the present embodiment is combined withEmbodiment 1, the separation layer 601 of the present embodiment may beused instead of the separation layer 409 of Embodiment 1, and the lasermay be radiated from the back side to perform the peeling.

Similarly, in the case where the present embodiment is combined withEmbodiment 2, the separation layer 601 of the present embodiment may beused instead of the separation layer 509 of Embodiment 2, and the lasermay be radiated from the back side to perform the peeling.

According to the present invention, crystallization is performed byradiating a laser beam across the entire surface of a substrate having abroad surface area while directing it at the location of a semiconductorregion which forms the TFTs, whereby a crystalline semiconductor layerhaving a large grain size can be formed and also improvement of the TFTcharacteristics is attained to realize a display having a curvedsurface.

According to the present invention, a display having a curved surface isrealized. Thus, in the case where an imaging or measuring display is tobe furnished in a limited space such as at the driver's seat in anautomobile or aircraft or other such vehicle, the display can be mountedto various locations that have curved surfaces (such as the window, theceiling, the door, the dashboard, etc.), thereby reducing the spaceoccupied by the display.

1. (canceled)
 2. A method for manufacturing a semiconductor devicecomprising a transistor comprising a semiconductor layer, the methodcomprising: forming a separation layer over a substrate; forming apeeled layer comprising the transistor over the separation layer; andirradiating the separation layer with a laser light to separate thepeeled layer from the substrate, wherein the peeled layer is capable ofcurving in a first direction, wherein a scan direction of the laserlight and a direction of a channel length of the semiconductor layer arefacing in a second direction, and wherein the first direction isperpendicular to the second direction.
 3. The method according to claim2, wherein the separation layer is formed of an amorphous silicon or apolysilicon.
 4. The method according to claim 2, wherein the separationlayer is formed by a sputtering method or a plasma CVD method so as toput a large amount of hydrogen into the separation layer.
 5. The methodaccording to claim 2, wherein the substrate is a glass substrate or aquartz substrate.
 6. The method according to claim 2, wherein elementsincluded in the peeled layer are formed at 410° C. or below.
 7. Themethod according to claim 2, wherein a shape of the laser light islinear or rectangular.
 8. The method according to claim 2, wherein thelaser light is irradiated to a back surface of the separation layerthrough the substrate.
 9. A method for manufacturing a semiconductordevice comprising a transistor comprising a semiconductor layer, themethod comprising: forming a separation layer over a substrate; forminga peeled layer comprising the transistor over the separation layer;irradiating the separation layer with a laser light to separate thepeeled layer from the substrate; and transferring the peeled layer to anobject, wherein the peeled layer is capable of curving in a firstdirection, wherein a scan direction of the laser light and a directionof a channel length of the semiconductor layer are facing in a seconddirection, and wherein the first direction is perpendicular to thesecond direction.
 10. The method according to claim 9, wherein theseparation layer is formed of an amorphous silicon or a polysilicon. 11.The method according to claim 9, wherein the separation layer is formedby a sputtering method or a plasma CVD method so as to put a largeamount of hydrogen into the separation layer.
 12. The method accordingto claim 9, wherein the substrate is a glass substrate or a quartzsubstrate.
 13. The method according to claim 9, wherein elementsincluded in the peeled layer are formed at 410° C. or below.
 14. Themethod according to claim 9, wherein a shape of the laser light islinear or rectangular.
 15. The method according to claim 9, wherein thelaser light is irradiated to a back surface of the separation layerthrough the substrate.
 16. The method according to claim 9, wherein theobject has a curved surface.